Uh oh: "Chief headline" of next IPCC report involves uncertainty growing 400% since 1988: 1% for James Hansen and his colleagues in 1988; 5% now

...now, according to Reuters, scientists are giving us a 95 percent confidence in this central conclusion of modern climate research. That appears to be the chief headline that will be emerging from the IPCC this time around....The report validates the increasingly popular skeptic claim that the rate of increase in global temperatures has "slowed" since 1998. In other words, temperatures are still going up, just not necessarily as quickly as previously.

The new report, Reuters says, offers only "medium confidence" that scientists understand the reasons for this slowing. Causes cited include the possibility that the oceans are taking up more heat, that volcanic eruptions (which tend to produce cooling) may be providing a partial offset to temperature rise, contributing too cooling, or that the climate itself has a lower "sensitivity" to greenhouse gas emissions than previously proposed.

[Revkin, 1988] This wasn't just a bad year, James Hansen of the NASA Goddard Institute for Space Studies told the Senate committee, or even the start of a bad decade. Rather, he could state with "99 percent confidence" that a recent, persistent rise in global tem­perature was a climatic sig­nal he and his colleagues had long been expecting.